share|improve this answer answered Apr 30 '09 at 15:43 Stephen C. Darn, forgot to adjust the amount of values define. up vote 28 down vote favorite 14 I'd like to implement an "assert" that prevents compilation, rather than failing at runtime, in the error case. permalinkembedsaveparentgive gold[–]pixelbeat_[S] 0 points1 point2 points 8 years ago*(0 children)As I pointed out in my article, BUILD_BUG_ON doesn't work at global scope.

The macro above will be useful for a long time to come though. It's because you have to specify the size of an array as a compile time constant. Still, assertions are extremely powerful; they can be viewed as "dynamic documentation," since they are checked at runtime. Acknowledgments Thanks to Ken Peters and Mike Teachman for helpful feedback on this article.

If the expression is true, it generates a typedef for an array of 1 char (which is harmless). First, it introduces a local namespace that avoids multiple redefinitions of the assert_static enumerator; second, it forces you to add a trailing semicolon after assert_static because the C Standard requires do/while In many places, we needed to check a status flag like this: #define UART_READY_MASK 0x80 #define IS_UART_READY() (gIOStatus & UART_READY_MASK) ... Browse other questions tagged verilog or ask your own question.

One trivial thing to do is check whether Boolean constants have been properly defined: assert_static(TRUE == 1 && FALSE == 0); Some projects employ ISO C99's portable integer types. Unfortunately, different platforms align and pad data differently, so a particular structure definition that lays out the members properly for one platform may produce an incorrect layout when compiled for a By using this check you can ensure that such conversions are safe: // Ensure that a pointer can safely be converted to an int assert_static(sizeof(pInBuffer) <= sizeof(int)); int myint = (int)pInBuffer; These are called static or compile-time asserts.

permalinkembedsaveparentgive gold[–]pointer2void 0 points1 point2 points 8 years ago(1 child)See also: http://www.jaggersoft.com/pubs/CVu11_3.html permalinkembedsavegive gold[–]pointer2void 0 points1 point2 points 8 years ago(0 children)and: http://www.embedded.com/columns/programmingpointers/164900888?_requestid=438985 permalinkembedsaveparentgive gold[–]Mignon -1 points0 points1 point 8 years ago(0 children)Bah, compile-time assert. A call of the form: assert(condition); expands to code that tests the condition. If your tools support mixed language, you could add a module that is just a VHDL entity with the necessary ports or generics and the obvious ASSERT statement. If you try to ct_assert() a non constant expression by mistake, this will also give an error and you can change to using a normal assert().

We introduce you to Apple's new Swift programming language, discuss the perils of being the third-most-popular mobile platform, revisit SQLite on Android , and much more! I knew that almost every compiler supports such a feature; however, I wanted to automatically alert developers porting the code to another platform. The first is the condition to assert is true, and the second is part of the type name declared behind the scenes. Do all aircraft need to have horizontal and vertical stabilizers?

Worse yet, over time, comments tend to get out of sync with the code they are supposed to clarify. I don't think anyone has written SDL binding, it should be quite easy, but I don't think most people see the point. I recommend that you try out different implementations until you find a solution that works best with your compiler(s). If you're a C++ programmer and you understand explicit template specialization, you might want to check it out.

It gives an "array can't be declared with size zero" compiler error each time the struct has an odd size. –Lundin Oct 16 '13 at 12:50 Yeah I read COMPILE_TIME_ASSERT(sizeof(the_struct) % 2 == 0); The real solution to your specific problem might however be to ensure that struct padding is enabled. Plain commentseven if embellished with words like "note" or "important"tend to be overlooked or misinterpreted by maintenance programmers. So the last piece of the puzzle is to put the compile time assertions inside a function. #include #define COMPILE_TIME_ASSERT(pred) \ switch(0){case 0:case pred:;} #define ASSERT_MIN_BITSIZE(type, size) \ COMPILE_TIME_ASSERT(sizeof(type) *

You would also get a slew of warnings about multiple declarations and unused variables if not in its own scope. –dreamlax Apr 30 '09 at 15:22 1 #define MY_COMPILER_ASSERT(EXPRESSION) do Unfortunately, the text of the error message that you see when an assertion fails varies with the compiler. Please take it to /r/ProgrammerHumor/. However, Dr.

Do you have something funny to share with fellow programmers? How do you express this assumption in code? This five-minute change worked fine and saved quite a bit of code and everyone was happyuntil we changed to a different hardware platform a year later. Constrained bit-fields struct-declarator: declarator declarator opt : constant-expression Reading the constraints of a bit field I see that if the width of a bit-field is zero the declaration cannot have a

As the MSDN documentation for assert states "(assert) Evaluates an expression and, when the result is false, prints a diagnostic message and aborts the program." There is another type of asserts Why did Vizzini have the wine and tablecloth all laid out? 80's or 90's sci fi movie title that has a mace? Please follow proper reddiquette. More Reading Boost static_assert has an even better implementation that takes cares of much more scenarios and compiler quirks.

While it is a good idea to leave assertions enabled as often and as long as possible, there are times when you have to switch them off; for instance, when you Just to be very clear here, I'm not suggesting that every assertion can be checked at compile time. A preferred method would be to use the sizeof operator, however that can't be used in the error checking, which I would really like to keep. They don't recognize enumeration constants in #if conditions, either.

These assumptions appeared so self evident that the programmer(s) took them for granted. Maybe wrapping it in curly brackets might fix it? Neat, huh? more hot questions question feed lang-vhdl about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation

This doesn't help C much. What's an easy way of making my luggage unique, so that it's easy to spot on the luggage carousel? Not the answer you're looking for? ISO C99 and ISO C++98 require chars to be signed.) If char happens to be unsigned, this test always evaluates to false.

Using assert to check the offset of a structure member defers until run time a check that should be done at compile time. And I am an external person and will be leaving here in a month or two. If the assertion fails (the #if condition is true), the preprocessor executes the #error directive, which displays a message containing the text in the directive and terminates the compilation. Why was Spanish Fascist dictatorship left in power after World War II?

In a nutshell, assertions are a means of automatically verifying assumptions made by developers; see Listing 1. This will also fail for all x<0, which are treated as "true" in C/C++ normally. Dobb's Archive Farewell, Dr. One answer is the declaration of an array cannot have a negative size.

You can exploit the requirement that constant array dimensions must be positive to implement compile-time assertions as a macro: #define compile_time_assert(cond) \ char assertion[(cond) ? 1 : 0] If x is Therefore, the developer should have used a dynamic assert instead: assert(gWriteMode != WRITE_MODE_READ); // Correct With static_assert implemented as 1/(e), the best a compiler can do in such a situation is

A defined boolean takes x memory this is then in the compiled program and cannot be changed. If those answers do not fully address your question, please ask a new question. 1 stackoverflow.com/questions/846103/runtime-vs-compile-time –Matt Whipple Oct 14 '12 at 13:01 add a comment| 5 Answers 5 active If you're a C++ programmer and you understand explicit template specialization, you might want to check it out. Colonists kill beasts, only to discover beasts were killing off immature mon...

share|improve this answer answered Feb 27 '12 at 20:38 jwddixon 734320 add a comment| up vote 9 down vote A runtime error happens during the running of the program. Sign in Share More Report Need to report the video? The best way to get to know those rules is to go through all the sections in the JLS containing the key words "compile-time error". Watch Queue Queue __count__/__total__ Find out whyClose Compile Time Vs Run Time Error KelliKOnline SubscribeSubscribedUnsubscribe99 Loading... ...

Dev centers Windows Office Visual Studio Microsoft Azure More... Finding and Fixing Errors Through Debugging Know Your Bugs: Three Kinds of Programming Errors Know Your Bugs: Three Kinds of Programming Errors Know Your Bugs: Three Kinds of Programming Errors Finding Not the answer you're looking for? Problem with tables: no vertical lines are appearing What will be the value of the following determinant without expanding it? You may need to use calculator to check the output. Reply Wit...

At runtime means, that you can compile your program just fine but at runtime, it throws an exception. share|improve this answer answered Jun 7 '14 at 19:48 user3708939 91 add a comment| up vote -1 down vote Run time means something happens when you run the program. Symbiotic benefits for large sentient bio-machine Circular growth direction of hair Arguments for the golden ratio making things more aesthetically pleasing What is this city that is being demoed on a A simple example would be a di...